Project description:Kentrophoros ciliates are found worldwide in coastal marine sediment, and have an obligate symbiosis with sulfur-oxidizing Gammaproteobacteria called Candidatus Kentron. The genomes of different Kentron species suggest that they are chemolithoheterotrophs, producing new biomass from organic carbon substrates. We investigated the metaproteome of Kentrophoros sp. H and its symbiont (from two sites in the Mediterranean), to verify that hypothesized pathways of carbon and energy metabolism are indeed expressed, and to estimate the stable isotope fractionation in biomass, which can be a signature of the carbon sources used by the organism.
Project description:Here, we report the use of Illumina RNA-Seq for investigating the physiology of the digestive-tract microbiome within the medicinal leech, Hirudo verbana. About 12 million cDNA reads were mapped against the genomes of the two dominant members of this simple microbiome. Results suggested that the most abundant, yet uncultured Rikenella-like bacterium forages host mucin glycans and ferments the carbohydrates to acetate that is secreted into the environment. The second dominant symbiont, Aeromonas veronii, appears to utilize the acetate secreted by Rikenella as a carbon and energy source, possibly linking the physiologies of the dominant symbionts. This study demonstrates how RNA-seq can be used to reveal the physiology of a naturally occurring microbiome.
Project description:Paracatenula are marine catenulid flatworms occuring in shallow water sediments. Adult Paracatenula lack a mouth and a digestive system. Instead, a trophosome containing intracellular alphaproteobacterial symbionts, namely Ca. Riegeria fill most of the worm´s body (Gruber-Vodicka et al., 2011). Paracatenula sp. ‘standrea’ that harbor Ca. Riegeria sp. 812A (standrea) were sampled in Elba, Italy in April 2016. Based on the genome of Ca. Riegeria sp. 812A (standrea) we discovered a versatile combination of storage and biosynthesis and a convergence with unrelated intracellular thiotrophic symbionts. Proteomic analyses were performed to investigate which symbiont genes related to the host nutrition were expressed.
Project description:Biological carbon fixation is foundational to the biosphere. Most autotrophs are thought to possess one carbon fixation pathway. The hydrothermal vent tubeworm Riftia pachyptila’s chemoautotrophic symbionts, however, possess two functional pathways: the Calvin Benson-Bassham (CBB) and the reductive tricarboxylic acid (rTCA) cycles. Little is known about how Riftia’s symbionts and related organisms coordinate the functioning of these two pathways. Here we investigated net carbon fixation rates, transcriptional/metabolic responses, and transcriptional co-expression patterns of Riftia pachyptila’s endosymbionts by incubating tubeworms at environmental pressures, temperature, and geochemistry. Results showed that rTCA and CBB transcriptional patterns varied in response to different geochemical regimes and that each pathway is allied to specific metabolic processes, suggesting distinctive yet complementary roles in metabolic function. Net carbon fixation rates were also exemplary, and accordingly we propose that co-activity of CBB and rTCA may be an adaptation for maintaining high carbon fixation rates, conferring a fitness advantage in dynamic vent environments.
